New micromachining techniques are being developed in recent years for increasingly higher integration and higher performance of large-scale integrated circuit (LSI). One such technique is Chemical Mechanical Polishing (CMP), the technique is often used for flattening of interlayer dielectric film layer, formation of metal plug and formation of embedded wiring in LSI production step, particularly in multilayer wiring forming step (see Patent document 1, for example).
One micromachining technique that has been employed is the “damascene method”, wherein a metal layer is accumulated on an insulating film having pre-formed trenches (recesses) and elevated sections (convexities) to embed the metal layer in the trenches, and then the metal layer accumulated on the elevated sections (the metal layer on sections other than the trenches) is removed by CMP to form embedded wiring (see Patent document 2, for example).
The common method of CMP for a metal layer involves attaching an abrasive cloth (abrasive pad) onto a circular polishing plate (platen), wetting the abrasive cloth surface with a polishing liquid, pressing the metal layer-formed surface of a base substrate against the abrasive cloth surface, rotating the polishing platen with a prescribed pressure (hereunder referred to as “polishing pressure”) applied to the metal layer from the back side of the base substrate, and removing the metal layer on the elevated sections by mechanical friction between the polishing liquid and the metal layer on the elevated sections.
A polishing liquid to be used for CMP of metal commonly comprises an oxidizing agent and a solid abrasive, it further comprises a metal oxide solubilizer or protective film-forming agent (metal corrosion preventing agent) as necessary. The basic mechanism of CMP employing a polishing liquid comprising an oxidizing agent is considered to be that, first, the metal layer surface is oxidized by the oxidizing agent to form an oxidation layer, and the metal layer is polished by shaving the oxidation layer with the solid abrasive.
In this polishing method, the oxidation layer at the surface of the metal layer accumulated on the elevated sections contacts with the abrasive cloth, and therefore shaving proceeds, whereas the oxidation layer at the surface of the metal layer that has accumulated on trenches only minimally contacts with the abrasive cloth, and is therefore not reached by the shaving effect of the solid abrasive. As CMP proceeds, therefore, the metal layer on the convexities is removed to flatten the substrate surface (see Non-patent document 1, for example).
It is known that constituent components for a CMP polishing liquid are different depending on the substance to be polished. For example, as a CMP polishing liquid wherein object to be polished is a layer composed of titanium nitride or tantalum nitride formed on substrates, a polishing liquid comprising protective film-forming agents and organic acids is known (see Patent document 3, for example).
Also, as a CMP polishing liquid to be applied for a layer composed of copper, for example, a polishing liquid comprising 2-quinolinecarboxylic acid is known (see Patent document 4, for example). As a CMP polishing liquid to be applied for a layer composed of nickel, for example, a CMP polishing liquid for HDD magnetic heads comprising abrasives, an organic acid and an oxidizing agent is also known (see Patent document 5, for example).